One of my friends likes to say this to believers of other faiths:
"I don't know all the answers. You don't know all the answers. Don't be a
d*ck."
Kinda cuts to the heart of just be a decent human regardless of which god
is the fad today or that you happen to root for.
My favorite saying is:
"We are both atheists, I just believe in one fewer god than you do. I
dismiss your god as you dismiss the others."
Some people have a hard time thinking that one through--it can be amusing
to watch them work it out.